Add script to automate reliable relocking

[mdekstrand]

This adds a shell script that runs conda-lock with the correct inputs and environment variables to ensure that locking is successful regardless of the user's local Conda configuration. It also tweaks a couple of dependency specifications to make sure that the main category contains a closure (conda-lock is not 100% on achieving that).

Once the upstream conda-lock bug is fixed, we can update this script to add the ability to update only our dependencies.

[mdekstrand]

This is failing the Docker test, because it does not have the code updates to use the poprox-concepts updates (those are in #35 I think), and the Docker image build does not use locked dependencies.

Once we use lockfiles for Docker image dependencies (which in the current setup would cause both Docker and local tests to fail in #35, not just local), then we'll be in a position where deployment and tests both reliably use the locked dependencies, and are consistent with local development.